Here's an excellent review by an IMDb poster. Excuse the length, but if you read it, I guarantee you'll be putting this title in your Netflix queue/Ziplist (if they carry it, of course):

An epic psychological thriller of awesome glamour. You can see why it made a bundle in its original release, and it should be more famous today.

La Piscine is about a cloistered foursome, trapped in a beautiful mansion on the French Riviera. This is what you might call a volatile mix, straight out of pagan Arcadia. Delon is Delon, which is to say, the height of male beauty; Birkin is a leggy, enigmatic nymph; Maurice Ronet is virile and conniving; and Romy Schneider -- looking like Candace Bergen with swimmer's muscles -- well, she is the question mark, the one who seems to have more conscience, more soul, and more class than the others, despite ( or because of ) being just slightly over the hill.

The first hour of this film consists of little more than this elegant quartet lounging around by the pool, playing records, showing their skin, drinking whiskey, playing cards. This may seem uneventful or trite but just try it yourself -- try to write a script with nothing but small talk for almost 60 pages, without feeling pressured to drive the plot forward except through the most delicate foreshadowings ( like when Ronet suggests Romy is aging and about to let herself go ). This first hour is crucial for atmosphere and this is a rare film where you really feel like you live it along with the characters.

We seem to be heading into Antonioni territory, as Ronet and his daughter Birkin plan to leave and Delon and Schneider are left facing the hollowness and superficiality of their connection. But then a death occurs and we are suddenly in a cheap mystery novel. The film zigs, and then zags back again with a great ending that reminds me of Rohmer in its bleak conclusion: Romantic codependency is spiritual death.

All the actors are great. Birkin deserves more credit for her bizarre confection, an awkward, nerdy girl who barely seems to notice she has grown into a supermodel's body, and who is still trapped mentally at the age of 12. Another reviewer complains about this, but the movie makes it clear that Ronet has kept her extremely sheltered. Romy Schneider is sympathetic without being as perfect an icy blonde as Carroll Baker. But that's the point. Carroll Baker, as a female Delon, would have been his match while Romy -- who is beautiful but flawed, bearing some physical signs of alcoholism -- is at a disadvantage, always losing in the game of who needs who the most. Maurice Ronet plays a man who is confident and full of bonhomie on the outside, but whose grimacing smile reveals all kinds of suppressed malice.

That being said, this is Delon's movie all the way. Purple Noon is the sketch of what would become a full-blown portrait in this movie. This is one of the richest, most detailed portrayals of a soulless psychopath I've ever seen, up there with Robert Montgomery in Night Must Fall or Jude Law in the recent Sleuth remake. Except Delon is far cooler, more natural than either.

Even emotionally, with words, he is like a snake that is languid for hours until it strikes quickly and fatally. When he first feels an attraction for Jane Birkin, Schneider notices and says, "Should I get ready to pack my bags and move out?" and Delon says, without flinching at all or showing any expression, "Not yet, let's wait a little while and see." With any other actor, you would wonder why Romy doesn't smack the S.O.B. and take off. With Delon, you know why she stays.

What makes this character different in Delon's gallery of pretty vipers is that this one starts out so normal. He walks like a normal person, he talks like a normal person, he has self-doubt and jealousy like a normal person, he is charming and approachable, yet sometimes, just for a brief second, the mask will drop and you'll see the kaleidoscopic fires of hellish insanity. Delon doesn't even seem to be acting, it's as if his every cell is straining toward the camera lens. The greater the narcissist, the greater the movie star.

IMDb: Walter Matthau is wonderful as the "philandering" dentist Dr. Julian Winston whose frequent fibs to girlfriend Goldie provide textbook proof of the dangers of lying. Goldie Hawn's touching kook Toni Simmons certainly deserved to win her Oscar. Ingrid Bergman's work as the stiff-as-starch nurse Stephanie is also touching to watch as she comes out of her shell, slowly and nervously.....With Goldie still plugging away, this film is an amazing link between the past and the present of movies, with over seventy years spanning Ingrid's first role and Goldie's most recent. Incredible.